New UNIX backend, mirage-platform/mirage-net

[Vincent Bernardoff <vb@xxxxxxxxxxxxxx>]

Hi all,

I would like any potential person interested in the UNIX-direct backend 
for Mirage to have a look at the changes I am going to introduce:
* In mirage-platform: https://github.com/mirage/mirage-platform/pull/43
* In mirage-net: https://github.com/mirage/mirage-net/pull/28

Basically, the changes remove the creation of virtual interfaces (tap) 
from mirage-platform, instead, mirage-platform will listen to a 
Lwt_stream in order to receive "vif infos", the stream itself being 
pushable via a function in OS.Netif (OS.Netif.add_vif).
The changes in mirage-net reflect those changes in mirage-platform, the 
Manager.create function now only takes a callback argument (the function 
to be called when new interfaces pop up), instead of giving optional 
arguments for OS.Netif.create to create something that has been 
requested by the manager. This is more consistent with how a unikernel 
under Xen gets its network interfaces via the XenStore.
It is now up to mirari (or code generated by mirari) to call 
OS.Netif.add_vif with a fd of a created/opened interface.

Haris, if you always work on openvswitch stuff on Mirage, you are 
probably the person the most concerned by those changes, I might have 
broken a bit your PCAP stuff, please tell me if you have any problem I 
would work with you to solve them.
Cheers,

Vincent

PS: This new backend comes with a new version of mirari whose release 
will follow very soon.